WO2016127716A1

WO2016127716A1 - Alloy material with high strength and ductility, and semi-solid state sintering preparation method therefor and uses thereof

Info

Publication number: WO2016127716A1
Application number: PCT/CN2015/099634
Authority: WO
Inventors: 杨超; 姚亚光; 康利梅; 刘乐华; 屈盛官; 陈维平; 李元元
Original assignee: 华南理工大学
Priority date: 2015-02-13
Filing date: 2015-12-29
Publication date: 2016-08-18
Also published as: US10344356B2; US20170137917A1; CN104674038B; CN104674038A

Abstract

An alloy material with high strength and ductility, and a semi-solid state sintering preparation method therefor and uses thereof. The preparation method comprises three steps: mixing powder, preparing alloy powder by high-energy ball milling, and carrying out semi-solid sintering on the alloy powder. The key is two-step sintering that comprises: heating below the melting temperature of the lowest-temperature melting peak of the alloy powder under the condition of sintering pressure, and carrying out sintering densification treatment; and releasing pressure, heating to the sintering temperature Ts, and carrying out heat preservation and carrying out semi-solid processing, wherein the sintering temperature is Ts; Ts is higher than or equal to the melting temperature of the lowest-temperature melting peak of the alloy powder; and Ts is lower than or equal to the melting temperature of the highest-temperature melting peak of the alloy powder.

Description

Description: A high strength and toughness alloy material and its semi-solid sintering preparation method and application

[0001] The invention belongs to the technical field of alloy material preparation, and particularly relates to a high strength and toughness alloy material and a semi-solid sintering preparation method and application thereof.

Background technique

[0002] Semi-solid metal processing refers to a processing method that utilizes a semi-solid temperature interval in a process in which a metal transitions from a solid to a liquid, or from a liquid to a solid. In the early 1970s, the Massachusetts Institute of Technology proposed the concept of semi-solid processing technology, which uses a non-dendritic semi-solid slurry to break the traditional dendritic solidification mode, with low deformation resistance and high material utilization. The unique advantages of easy automation and the formation of new processing technologies have attracted the attention of researchers from all over the world, and the products and applications of semi-solid processing have also developed rapidly.

[0003] However, as of now, the research on semi-solid processing technology mainly focuses on low-melting alloy systems such as aluminum alloys and magnesium alloys, and the microstructure of the prepared alloys is relatively coarse. At the same time, it is impossible to obtain fine grained microstructures such as ultrafine or nanocrystalline by conventional semi-solid processing methods (such as rheocasting, rheological forging, and thixotropic forging), and it is even more impossible to prepare fine crystals. A two-scale microstructure in which two or more of the three structures, superfine or nanocrystalline, coexist. In fact, the results show that the two-scale microstructures present in iron, titanium, aluminum and their alloys tend to significantly improve the overall performance of bulk materials. Furthermore, the preparation of slurry or blank in the conventional semi-solid processing method is complicated, and the preparation of the semi-solid slurry of the high melting point alloy is difficult, which limits the semi-solid processing in the high melting point alloy system such as titanium alloy and nickel alloy. Research and application.

[0004] In recent years, researchers have obtained a series of nano-scale matrix/amorphous matrix + micron-scale ductile β-Ti dendrites of two-scale titanium alloy by copper die casting rapid solidification. In the deformation process, the nanocrystalline matrix/amorphous matrix provides ultra-high strength, while the ductile β-Ti dendrites contribute to the high plasticity of the material, and the fracture strength is greater than 2000 MPa and the fracture strain is greater than 10%. Since then, more and more high-strength alloy systems (including Fe-based, Zr-based, and Ti-based, etc.) having such microstructures have been reported. The core of this preparation method is to carefully design the alloy composition and precisely control the solidification conditions of the alloy melt [G. He, J. Eckert, W. Loser, and L. Schultz, Nat. Mater. 2, 33 (2003)], selecting a suitable incubation zone during the solidification process to allow the β-Ti phase to preferentially nucleate to form dendrites, and then to leave the remaining alloy melt fast. Cooling forms a nanocrystalline or amorphous matrix. However, this method also has two defects: First, because the five component components are easy to form intermetallic compounds, thereby canceling the dendrite enhancement effect and deteriorating the ductility of the material, thereby forming a nanocrystalline matrix/amorphous matrix + ductile β- The composition range of Ti dendrites is relatively narrow; the second is the limited cooling rate during the copper mold casting process, which results in the preparation of these high-strength and tough double-scale titanium alloys, which are generally several millimeters (4 mm or less). The above two factors have become the bottleneck restricting the practical application of these high-strength and tough double-scale titanium alloys.

[0005] As an alternative forming technology, the powder metallurgy technology has the characteristics of uniform material composition, high material utilization rate, near net shape formation, and easy preparation of ultrafine/nanocrystalline high strength and toughness alloy, which is often used for preparation. Large-sized, complex-shaped alloy parts. Regarding the combination of semi-solid processing technology and powder metallurgy technology (such as powder forging, powder extrusion, powder rolling, etc.), the low melting matrix alloy particles are usually mixed with high melting point reinforcing phase particles and heated to a semi-solid range of the base alloy. The composite material is prepared by stirring and further processing. However, due to the inherent defects of the additive reinforcing phase of the composite material, the wettability of the matrix alloy is poor, and the semi-solid powder metallurgy method is difficult to ensure uniform distribution of the second phase in the matrix, so semi-solid processing combined with powder metallurgy technology is prepared. There is a significant increase in the performance of composite materials.

[0006] In view of this, if a semi-solid processing technology can be used in a high-melting-point alloy system such as a titanium alloy to obtain a novel nanocrystalline, ultrafine crystal, fine crystal or even a double-scale microstructure, a new high performance and high performance will be obtained. The melting point alloy material and its engineering parts for industrial applications provide a novel preparation method.

technical problem

In order to overcome the above disadvantages and disadvantages of the prior art, a primary object of the present invention is to provide a semi-solid sintering preparation method of a high strength tough alloy material. The method can prepare high-strength and high-melting-point alloys and parts thereof with large size, complicated shape, microstructure, nanocrystalline, ultrafine crystal, fine crystal or double-scale structure, and overcome the traditional semi-solid processing technology, difficult to prepare semi-solid slurry It is difficult to obtain nanocrystalline, ultrafine, fine or double-scale structures, and it is difficult to obtain large-sized bulk materials by rapid solidification.

Another object of the present invention is to provide a high strength and toughness alloy material prepared by the above method.

[0009] Still another object of the present invention is to provide the above-mentioned high-strength and tough alloy materials in aerospace, military, instrumentation Apps in the domain.

Problem solution

Technical solution

[0010] The object of the invention is achieved by the following scheme:

[0011] A semi-solid sintering preparation method for a high-strength and toughness alloy material, which is a combination preparation method of powder metallurgy technology and semi-solid processing technology, specifically comprising the following steps and process conditions:

[0012] Step 1: Mixing powder

[0013] According to the designed alloy composition, the elemental powder is placed in a proportioned manner in a mixer to be uniformly mixed.

[0014] Step two: high energy ball milling to prepare alloy powder

[0015] placing the uniformly mixed powder in a ball mill for high energy ball milling until an alloy powder of nanocrystalline or amorphous structure is formed;

[0016] Step 3: Semi-solid sintered alloy powder

[0017] The alloy powder loaded into the sintering mold is fixed by powder metallurgy technology, and the sintering temperature Ts is selected, and the sintering is performed by a two-step method: heating under the sintering pressure condition to below the melting temperature of the melting point of the lowest temperature of the alloy powder, the alloy is The powder is subjected to sintering densification treatment; after depressurization, the temperature is raised to the sintering temperature Ts and the semi-solid processing is performed by heat preservation, and the process conditions are as follows:

[0018] sintering temperature Ts: Ts ≥ alloy powder minimum temperature melting peak melting temperature

[0019] ^ ≤ alloy powder highest temperature melting peak of the melting temperature;

[0020] sintering pressure is 20~500 MPa;

[0021] Cooling to obtain a high strength and toughness alloy material.

[0022] Preferably, when the sintering mold used is a graphite mold crucible, the sintering pressure in step 3 is preferably 30 to 50 MPa; when the sintering mold used is a tungsten carbide mold, the sintering pressure in step 3 is preferably 50~ 500 MPa.

[0023] The melting temperature of the melting point of the lowest temperature melting peak of the alloy powder in the preparation method of the present invention and the maximum melting temperature of the melting peak of the alloy powder are obtained by thermal physical property analysis of the alloy powder after the ball milling in the second step. Two or more melting peaks are obtained in the thermal property analysis, as well as the initial melting temperature, the peak melting temperature, and the ending melting temperature of each melting peak.

[0024] The powder metallurgy technology described in the third step refers to any powder metallurgy technology conventionally used in the art, It is any one of methods such as powder extrusion, powder hot pressing, powder rolling, powder forging, and spark plasma sintering.

[0025] The elemental powder in the first step may be a simple powder which is conventionally used for the preparation of the alloy in the field, and may be a powder prepared by various methods such as an atomization method, an electrolysis method, a hydrogenation dehydrogenation method, etc., and the particle size is not specifically limited. It may be a fine powder or a relatively coarse powder. The alloy composition of the design refers to the alloy component obtained by the target.

[0026] The conditions of the high-energy ball milling in the second step are not specifically limited, and it is only necessary to achieve the effect of ball-milling to form an alloy powder of a nanocrystalline or amorphous structure. The ball milling is carried out under an inert gas atmosphere, preferably under argon gas protection.

[0027] The heat preservation time described in the third step may be adjusted according to actual conditions, and is preferably 2 to 10 minutes.

[0028] The high-strength and toughness alloy material prepared in the third step can also be subjected to subsequent heat treatment, for example, the prepared high-strength and toughness alloy material is placed in a vacuum furnace, and subjected to annealing treatment to eliminate residual stress and microstructure defects.

[0029] The high-strength and toughness alloy materials prepared by the above method may be different alloy systems according to design, including Ti-based, Ni-based, Z-based, Cu-based, Co-based, Nb-based, Fe-based, Mn-based, Mo-based Alloy systems such as Ta-based, especially high-melting alloy systems such as Ti-based and Ni-based. The high-strength and toughness alloy material prepared by the invention has a new structure, and the structure comprises nanocrystalline, ultrafine crystal, fine crystal or double-scale structure, so has excellent performance and can be widely applied to aerospace, military, instrumentation. In the field.

[0030] The principle of the invention is:

[0031] The preparation method of the present invention can perform semi-solid processing on various alloy systems, especially high-melting alloy systems such as Ti-based and Ni-based, thereby obtaining nanocrystalline, ultrafine crystal, fine crystal or double-scale structures, and the like. A new type of microstructure and excellent alloy properties. The preparation method of the invention is a combination preparation method of powder metallurgy technology and semi-solid processing technology, the core of which is that by measuring the melting peak of the alloy powder, the temperature range of the two-step sintering is selected, thereby sintering and densifying the alloy powder. The semi-solid processing is performed, and the sintering temperature is between the initial melting temperature of the melting peak of the lowest temperature and the initial melting temperature of the melting peak of the highest temperature, and the sintering pressure is between 30 and 500 MPa. The invention overcomes the problems of traditional semi-solid processing technology, difficult to obtain double-scale structure, and is suitable for preparing high-strength and tough alloy materials and parts thereof which are large in size, complex in shape and suitable for engineering applications, and has wide versatility and practicality. Sexuality has a good prospect of popularization and application in the fields of aerospace, military, instrumentation and so on. Advantageous effects of the invention

Beneficial effect

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] (1) The preparation method of the present invention can perform semi-solid processing on a plurality of alloy systems, particularly a high-melting alloy system which is rarely studied such as a Ti-based or Ni-based, thereby obtaining nanocrystalline, ultrafine crystal, New microstructures and excellent alloy materials such as fine-grained or double-scale structures have important theoretical and engineering significance for expanding semi-solid processing.

[0034] (2) The powder metallurgy technique used in the preparation method of the present invention may include any one of powder extrusion, powder hot pressing, powder rolling, powder forging, and discharge plasma sintering, and thus can be used for preparing a large size. High-strength alloys and their parts with complex shapes and suitable for engineering applications have wide versatility and practicability.

[0035] (3) The high-strength and toughness alloy material prepared by the invention has a microstructure including nanocrystals and ultrafine crystals.

, fine crystal or double-scale structure, with more excellent performance.

[0036] (4) Compared with the conventional semi-solid processing method, the invention solves the problem of difficult pulping, and can directly perform ball milling and powder sintering according to the designed alloy composition, thereby greatly saving the processing cost of the raw material.

[0037] (5) Compared with a copper mold casting method capable of producing only a small-sized high-strength alloy, the present invention can produce a high-strength alloy and a part thereof which are large in size, complicated in shape, and suitable for engineering applications.

[0038] (6) Compared with the composite materials prepared by the current powder metallurgy semi-solid processing technology, the various phases obtained by the invention belong to in-situ precipitation, and there is no problem of poor wettability between the phases, thus the prepared The alloy has better performance.

Brief description of the drawing

DRAWINGS

1 is a differential scanning calorimetry curve of the high energy ball milling alloy powder prepared in Example 1.

2 is a scanning electron micrograph of a high-strength and tough double-scale titanium alloy prepared in Example 1.

3 is a transmission electron micrograph of a high-strength and tough double-scale titanium alloy prepared in Example 1.

4 is a stress-strain curve of a high-strength and tough double-scale titanium alloy prepared in Example 1. [0042] FIG. BEST MODE FOR CARRYING OUT THE INVENTION

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

Example 1 : Preparation of a High Strength and Toughness Double-Scale Structure Titanium Alloy

[0045] The semi-solid sintering preparation method, the specific steps are as follows:

[0046] Step 1: Mixing powder

[0047] The Ti ₆₂ Nb ₁₂ . ₂ Fe ₁₃ . ₆ Co ₁₃ . ₆ A1 ₅ . ₈ alloy system is selected, and the powder is compounded according to the mass ratio of the selected alloy system. In this example, the atomization method is adopted with a particle size of 7.5 μηι. The elemental powder of the present invention is not limited thereto, and the elemental powder may be a powder prepared by other methods such as electrolysis, and the particle size is not particularly limited, and may be a fine powder or a relatively coarse powder. The above elemental powder was uniformly mixed in a mixer. The present example is preferably a Ti-based alloy system, but the alloy system selected in the present invention is not limited thereto, and may also be selected from a Ni group, a Zr group, a Cu group, a Co group, a Nb group, a Fe group, a Mn group, a Mo group, and a Ta group. And other alloy systems.

[0048] Step 2: Preparation of alloy powder by high energy ball milling

[0049] The uniformly mixed powder is placed in an argon-protected planetary ball mill (QM-2SP20) for high-energy ball milling, and the ball milling media such as the can body and the grinding ball material are all stainless steel, and the diameters of the grinding balls are 15, 10, and 6 mm, respectively. They have a weight ratio of 1:3:1. The high-energy ball milling process parameters are as follows: The ball mill tank is filled with high-purity argon (99.999 %, 0.5 MPa) protection, the ball-to-batch ratio is 8:1, and the rotation speed is 2 s. It is taken in the glove box in an argon atmosphere every 10 h. The left and right powders were tested by X-ray diffraction (XRD) and differential scanning calorimetry (DSC) until 70 h after ball milling, and XRD showed 70

h The powder structure of the ball mill is surrounded by β-Ti nanocrystals with an amorphous phase of about 90 <3⁄4. The DSC curve of Figure 1 indicates that the 70 h ball milled powder has an endothermic peak temperature of 1125 ° C during heating and Two melting peaks at 1180 °C.

[0050] Step 3: Semi-solid sintered alloy powder

[0051] Take 20 g of the alloy powder prepared in the second step, into a graphite sintering mold with a diameter of Φ 20 mm, pre-press the alloy powder to 50 MPa through the positive and negative graphite electrodes, evacuate to 10 - ² Pa, and then charge High purity argon gas protection; rapid sintering with pulse current, the process conditions are as follows: Sintering equipment: Dr. Sintering SPS-825 spark plasma sintering system

Sintering mode: pulse current

[0054] Pulse current duty cycle: 12:2

Sintering temperature Ts: 1100 ° C

[0056] Sintering pressure: 50 MPa

[0057] Sintering sinter: Under 50 MPa pressure, the temperature is raised to 1050 ° C in 10 minutes, and the temperature is raised to 1100 under pressure relief conditions for 1 minute.

°C and keep it for 5 minutes.

[0058] After sintering, a high-strength and tough double-scale structural titanium alloy material having a diameter of Φ20 mm (if the mold size is larger, the alloy material is larger in size) and having a density of 5.6 g/cm 3 is obtained. The SEM image of Figure 2 shows that the microstructure consists of a micron-sized (CoFe) Ti ₂ ffi region and a micron-sized hybrid matrix. The TEM image of Figure 3 shows that the micron-sized hybrid matrix is surrounded by nano-sized β-Ti. The size of TiFe is composed, so the alloy is a double-sized structure including microcrystalline (CoFe) Ti ₂ , nanocrystalline β-Ti and TiFe; the compressive stress-strain curve of Fig. 4 indicates the compressive yield strength of the double-scale titanium alloy material. The strain at break and the strain at break are 1790 MPa and 19%, respectively.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and modifications may be made without departing from the spirit and scope of the invention. Simplifications, which are equivalent replacement means, are included in the scope of the present invention.

Claims

Claim

A semi-solid sintering preparation method for a high-strength and toughness alloy material, characterized in that the following steps and process conditions are specifically included:

Step 1: Mixing powder

According to the designed alloy composition, the elemental powder is proportioned and placed in the mixer to be evenly mixed; Step 2: High energy ball milling to prepare the alloy powder

The uniformly mixed powder is placed in a ball mill for high energy ball milling until an alloy powder of nanocrystalline or amorphous structure is formed;

Step 3: Semi-solid sintered alloy powder

The alloy powder packed in the sintering mold is consolidated by powder metallurgy technology, and the sintering temperature Ts is selected and sintered by a two-step method: the sintering temperature is raised to below the melting temperature of the melting point of the lowest temperature of the alloy powder, and the alloy powder is sintered. Densification treatment; After depressurization, the temperature is raised to the sintering temperature Ts and the semi-solid processing is performed by heat preservation. The process conditions are as follows: Sintering temperature Ts: Ts ≥ the melting temperature of the melting peak of the lowest temperature of the alloy powder

^ ≤ alloy powder maximum temperature melting peak melting temperature;

Sintering pressure is 20~500 MPa;

Cooling to obtain a high strength and toughness alloy material.

The semi-solid sintering preparation method of the high-strength and toughness alloy material according to claim 1, wherein: when the sintering mold used is a graphite mold crucible, the sintering pressure in the third step is 30 to 50 MPa; when the sintering mold is used The tungsten carbide mold 吋, the sintering pressure in the third step is 50 to 500 MPa.

The semi-solid sintering preparation method of the high-strength and toughness alloy material according to claim 1, wherein the powder metallurgy technology described in the third step is powder extrusion, powder hot pressing, powder rolling, powder forging and discharge plasma sintering. Any of them.

The semi-solid sintering preparation method of the high-strength and toughness alloy material according to claim 1, wherein the elemental powder described in the first step is a powder prepared by an atomization method, an electrolysis method or a hydrodehydrogenation method.

The method for preparing a semi-solid sintered high-strength alloy material according to claim 1, wherein The invention is as follows: the high strength and toughness alloy material prepared in the step 3 is subjected to subsequent heat treatment.

[Claim 6] The semi-solid sintering preparation method of the high-strength and toughness alloy material according to claim 1, wherein the high-strength and toughness alloy material prepared in the third step is annealed.

[Claim 7] A high-strength alloy material obtained by a semi-solid sintering preparation method of the high-strength alloy material according to any one of claims 1 to 6.

[Claim 8] The high-strength alloy material according to claim 7, wherein the high-strength alloy material is Ti-based, Ni-based, Zr-based, Cu-based, Co-based, Nb-based, Fe-based, and Mn-based. , Mo-based or Ta-based alloy systems.

[Claim 9] The high-strength and toughness alloy material according to claim 7, wherein the structure of the high-strength alloy material comprises a nanocrystalline, ultrafine, fine or double-scale structure.

[Claim 10] The use of the high-strength alloy material according to any one of claims 7 to 9 in the field of aerospace, military and instrumentation.